Photographic apparatus for processing sheets of photosensitive material by immersing them in a processing solution are well known in the art. It is also known in the art that the chemical reactions that occur when the photosensitive material is immersed into these processing solutions quickly exhaust or very nearly exhaust the active chemical agents nearest the surface of the film. It has therefore been found that improved processing results if the solution is agitated during the processing operation. Although many ways are known for agitating a processing solution, one well known way utilizes gaseous burst agitation in which bursts of nitrogen gas or the like are released at controlled intervals through openings in a distributor disposed in the solution at the bottom of the processing tank. When first released, the bursts impart a sharp displacement pulse or piston action to the entire volume of solution, and then as the bubbles make their way to the surface they provide a localized agitation around each bubble.
An earlier gaseous burst type device used in photographic processing is disclosed and illustrated in U.S. Pat. No. 3,291,025, incorporated herein by reference. The device uses a single distributor for emitting a gas into the processing solution in a simultaneous burst. Other processing apparatus that utilize some sort of solution agitator are disclosed in U.S. Pat. Nos. 4,248,513 and 3,180,243. In each of these prior art processes, the gaseous burst occurs simultaneously throughout the distributor such that the distributor acts like a single unit. Additionally, the inlet ports are themselves simultaneously charged with a gas and, thus, function as a single delivery system.
A major drawback of the earlier processing apparatus is that they are known to produce nonuniform agitation patterns in the processing solution thereby resulting in sensitometric variations on simultaneously processed film. This has been known to occur in both `rack and tank` and deep tank photographic development processes. Another drawback in both `rack and tank` and in deep tank processing, is that nonuniform agitation results when the film strips are not rotated in the solution during processing. In either case, nonuniform agitation of the solution results in sensitometric variations in simultaneously processed photosensitive material. In aggravated cases, the nonuniformity of the development reaction may manifest itself as streaks or mottle in the developed photographic image.
Consequently, a need exists for an apparatus capable of producing uniform agitation in photosensitive sheet processing devices which will result in significantly reduced sensitometric variation in simultaneously processed photosensitive sheets.